Drill ships and semi-submersible drilling rigs are often used for subsea well intervention operations. The deck layout on the known vessels serving such multiple functions is primarily designed for drilling operations, while less attention has been given to optimizing equipment handling related to well intervention work.
An example of a prior art multi-purpose (drilling, well intervention) ship is illustrated in FIG. 1 (partly shown). The ship 1 has a drilling module 4a comprising a drilling derrick 3 placed on a drill floor 4b above a moon pool (not shown). The ship also comprises a blow-out preventer (BOP) 9a, a BOP deck 9b, and a riser storage compartment 6 for holding a number of risers 5. A riser crane 7 with an operator's cabin 11 hoists the individual riser up from the riser storage compartment, where they are stored horizontally, and positions it on the riser transporter 12, which transports the riser into the derrick and upends the riser on the drill floor. A pipe deck 28 is arranged forward of the drilling module.
In a normal mode of operation, intervention equipment (not shown) is placed on the main deck 2, from where it is lifted up and onto the elevated drill floor 4b by the deck crane 8 as and when this equipment is being used for subsea well intervention. Equipment has to be transported into the drill floor or surrounding area from the main deck in a time consuming, piece-by-piece basis, and much of the rigging for these operations requires operations in well-centre (online) to be stopped.
The present applicant has devised and embodied this invention in order to overcome shortcomings of the prior art, and to obtain further advantages.